Lung infection Flashcards
What are types of multi-layered defence mechanisms?
Mechanical
Local
Systemic
Give example of mechanical
Pathogens stick onto the mucus within the airways (hairs in the nose also filter things out)
examples of local?
Bronchus associated lymphoid tissue (BALT)- there is an immune system within the respiratory tract that samples antigens that you inhale and produce antibody to neutralise it.
what happens if a bug gets past the mechanical and local defences?
- Call upon defences from the circulation (polymorphonuclear leukocytes).
- Neutrophils can mobilise themselves from the circulation, move into the airways and attack the infectious agent
What structures knit the epithelia into a cohesive layer?
Tight junctions
what type of cell produces mucus
Epithelium is made up of ciliated cells and goblet cells which produce mucus along with submucosal glands.
Describe the two layers of fluid surrounding and above the cilia.
Watery periciliary fluid
Mucus (thick and gel-like)
How fast does each cilium beat?
15 times per second
Describe how the cilium is withdrawn after the forward stroke.
It is withdrawn in a curved fashion within the periciliary fluid and under the mucus so that it doesn’t pull the mucus back in the opposite direction.
Describe the rhythm of the cilia.
Metachronal rhythm
Describe the ultrastructure of the cilium.
It has a 9+2 structure - it has 9 microtubule pairs around the outside and two microtubules in the middle
The outer microtubule pairs have inner and outer dynein arms
What enables the cilia to move?
ATPase on the dynein arms, which provides energy for the microtubules in the cilium to move up and down each other to make the cilia bend
what 2 things must you take into consideration if someone presents with chest infection?
- the infection itself
- the host defences
Give two examples of acquired defects of the mucociliary system.
Smoking and
Viral infections
Why do bacterial infections often follow viral infections?
Viruses can damage the epithelia allowing the bacteria to dock down and colonise
What can happen to the cilia when they grow back?
They can regrow abnormally and form compound cilia, which are useless
What is the relationship between cilia and dextrocardia?
50% of people born without functioning cilia have dextrocardia
This is because the micro-tubules are involved in guiding cells around during embryological development.
in some patients, there is an inner dynenin arm but NO outer dynenin arm. This is the DYNEIN ARM EFFECT
how does dectrocardia look on an x-ray?
-the side of the body that the heart is on is RANDOM
What is the term given for congenital disease causing malfunctioning cilia? How does this disease affect the ultra-structure of the cilium?
Primary ciliary dyskinesia - this is caused by a dynein arm defect
What biochemical marker is used to assess risk of primary ciliary dyskinesia before performing nasal biopsy?
People with primary ciliary dyskinesia have lower levels of nasal nitric oxide than people without.
What is the most common cause of bronchitis and sinusitis?
Haemophilus influenza
What parts of the epithelium does bacteria stick to?
Damaged areas of epithelium - they do not stick to the ciliated epithelium
How does pneumonia look like on an x-ray and what happens in pneumonia?
-There is pneumonia in the superior lobe of the right lung
-this is actually SOLID lung: the alveoli are full of pus.
-alveoli are full of pus
pus= debris of the host trying to fight the infection
what are the clinical features of pneumonia?
- cough
- sputum
- fever
- dysponoea
- pleural pain
- headache
-get a stabbing pleuritic chest pain
what is special about the bacteria that causes pneumonia?
- it has a polysaccharide capsule around it
- the capsule is negatively charged, which makes it more difficult for the bug to bind to the epithelium but it also makes it much more virulent and able to invade the bloodstream and cause systemic infection.
What happens to the protease and anti-protease ratio in chronic inflammation?
During phagocytosis, a little bit of protease gets spilled into the surrounding secretions.
- usually there are anti-proeases to neutralise the enzyme and stop it causing damage
- in chronic there are so many neutrophils in the lungs and so much protease is released that the protease enzyme overwhelms the antiproteases. As the antiproteases are overwhlemed, you get FREE PROTEASES sitting in the yellow-green sputum, which causes damage.
